User guide

EDA System Services
1/1551-HSC 901 35/3 Uen C 2005-12-02
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QinQ is used for the following reasons:
• To be able to preserve an existing tagging of the traffic from the End-
user or a sub-provider.
• To enable the re-use of the VLAN IDs, thereby extending the amount of
used VLANs above 4096.
The QinQ can be used with any Access Method. Figure 35 on page 47
illustrates the QinQ principle.
Ethernet Access Domain
IP
DSLAM
Local loop
Data
Ethernet
header
Sub.
VLAN
Inner
VLAN
Data
Ethernet
header
Outer
VLAN
Sub.
VLAN
Legend:
Mandatory
Optional
Figure 35 Using QinQ in EDA
When a frame from the End-user reaches the Access node, one (outer) or
two (inner and outer) VLAN tags are added to the frame. The frame is sent
into the Access Domain Ethernet where the outer VLAN tag is used as the
VLAN ID, priority and Ether type. When the frame leaves the Access
Domain both VLAN tags are removed (either by an IP DSLAM or by a
router. However, the node can read the inner VLAN tag and use the
information further if so required.
Figure 36 on page 48 illustrates one way of using the QinQ for VLAN per
End-user, while using the same VLAN for a service.